Forward Flow Test

byMichael O'BrianonFebruary 24, 2009

Back flow Devices Need to be Tested at Full Flow

Backflow devices are intended to prevent that nasty sprinkler water from going into your drinking water. These devices need some tender loving care in order to operate efficiently and test must be conducted to ensure they can open to meet the system demand. In the 2002 edition of National Fire Protection Association (NFPA) 13, Standard for the Installation of Automatic Fire Sprinkler Systems, a testing requirement was added for the forward flow testing of back-flow devices.

In fire protection systems, the back flow device is installed below the system control valves and can be the cause of reduced flow for the system. Reduced flow can occur if the system is not properly designed to include the device or tested to ensure the system flow is not reduced. The device is regulated by the local plumbing code for the protection of the water system.

NFPA 13 Section 24.2.5 states (2007 edition):

The backflow prevention assembly shall be forward flow tested to ensure proper operation. The minimum flow rate shall be the system demand, including hose stream allowance where applicable.

The user is also referred to 8.17.4.6 for clarification on the installation of these devices. Although the requirement was published starting in 2002 (the most current standard is 2007) many sprinkler contractors and inspectors are unaware of the requirement.

Unfortunately there is no one size fits all answer for this code requirement. It is important to understand that sprinkler system may have multiple design capacities. When sizing for the forward flow test, the highest demand (GPM) with the hose allowance should be utilized. This information can be obtained from the cover sheet of the hydraulic calculation or the hydraulic design placard.

When plans are submitted and reviewed by the local building or fire department, the reviewer should verify the details provided by the designer. Details should include maximum system flow (based on the hydraulic calculations) and details on the test equipment configuration including size and number of outlets.

There are several common options available and which include (but not limited to):

A bypass may be installed around the check valve installed in the piping between the system and Fire Department Connection (FDC). The bypass would include a supervised valve in the normally closed position. During testing the contractor would flow out the outlet of the fire department connection through the appropriate hose and nozzle configuration

Install various outlets on the system side of the back-flow device. The outlets would look similar to a hose or 2.5” standpipe connection.

Provide a test header, similar to those on systems which utilize a fire pump.

A good rule of thumb is that a 2.5” connection can accommodate approximately 250 gpm. Shop drawings for sprinkler systems can easily identify this requirement in the riser detail.

Acceptance Test Procedures

During the acceptance testing of a new system, the contractor will install various hose lines to the outlets and include appropriate orifices on the end of the line. The lines must be secured from movement and the lines should discharge to an area that can accommodate the flow of water and not damage the area.

The valves will be slowly opened, a pitot gauge utilized to ensure the design flow is met. Assuming the system flows at the design rate the device passes. When the desired rate is not achieved, the contractor shall inspect the system for defects and develop a strategy to remedy the situation. The contractor shall indicate the flow and test conducted on the completion documents. During initial acceptance tests the forward flow of the back flow should be conducted after the velocity flush test of the under ground piping (would reduce damage to the device).

We have noticed that this requirement is not easily known by the industry and can include some added cost to the system design. The forward flow test ensures that the backflow devices can operate at the system design.

The safety considerations during the test can not be understated. Contractors, inspectors, and witnesses should ensure proper procedures are identified. The lines shall be properly secured from movement. This may include utilizing devices such as a hose monster or a secure bracket that can hold multiple lines. Flow of 300 gpm at 70 psi can create significant discharge issues if not properly addressed. Utilizing additional staff who are able to shut down the line quickly is a great practice.

Not only is this a requirement of NFPA 13 but it is also a requirement of NFPA 25. The section below is from the 2002 edition.

12.6.2 Testing.

12.6.2.1* All backflow preventers installed in fire protection system piping shall be tested annually in accordance with the following:

(1) A forward flow test shall be conducted at the system demand, including hose stream demand, where hydrants or inside hose stations are located downstream of the backflow preventer.

(2) A backflow performance test, as required by the authority having jurisdiction, shall be conducted at the completion of the forward flow test.

A.12.6.2.1 The full flow test of the backflow prevention valve can be performed with a test header or other connections downstream of the valve. A bypass around the check valve in the fire department connection line with a control valve in the normally closed position can be an acceptable arrangement. When flow to a visible drain cannot be accomplished, closed loop flow can be acceptable if a flowmeter or sight glass is incorporated into the system to ensure flow.

12.6.2.1.1 For backflow preventers sized 50.8 mm (2 in.) and under, the forward flow test shall be acceptable to conduct without measuring flow, where the test outlet is of a size to flow the system demand.

12.6.2.1.2 Where water rationing shall be enforced during shortages lasting more than 1 year, an internal inspection of the backflow preventer to ensure the check valves will fully open shall be acceptable in lieu of conducting the annual forward flow test.

12.6.2.1.3 Where connections do not permit a full flow test, tests shall be completed at the maximum flow rate possible.

12.6.2.1.4 The forward flow test shall not be required where annual fire pump testing causes the system demand to flow through the backflow preventer device.

12.6.2.2* All backflow devices installed in fire protection water supply shall be tested annually at the designed flow rate of the fire protection system, including required hose stream demands.

A.12.6.2.2 The tests required by 12.6.2 typically test only for operation of the device under backflow conditions. Forward-flow test conditions are required by other portions of this standard.

12.6.2.2.1 Where connections do not permit a full flow test, tests shall be conducted at the maximum flow rate possible.

12.6.3 Maintenance.

12.6.3.1 Maintenance of all backflow prevention assemblies shall be conducted by a trained individual following the manufacturer’s instructions in accordance with the procedure and policies of the authority having jurisdiction.

12.6.3.2 Rubber parts shall be replaced in accordance with the frequency required by the authority having jurisdiction and the manufacturer’s instructions.

For folks who follow the 2008 version of NFPA 25 it is in chapter 13.6.2.

Insurance LC Rep
Great continuation of the article, with the NFPA 25. One the items that NFPA 25 brings up is the follow up forward flow test beyond the initial acceptance test. Even NFPA 25 says forward flow test at design flow, how do you interpret that?

Existing system if you can flow water that is close to the demand, then great, if not flow as much as you can. What I look for is they place calibrated gauges on the device and then compare the flow to the loss the mfg of the devise says it should be. Say you can flow 500 gpm and the mfg says at 500 gpm the loss should be 4 psi, if they get 4 psi great, if it is 8 psi, time to take the device apart.

I’m sure he means the installer, or manufacturer’s rep (or other authorized persons), would be opening the device up to inspect for a cause for the problem. The AHJ should not even consider touching a device for liability reasons. ALWAYS have qualified personnel onsite to operate valves and make the appropriate corrections, if needed. Two goals: Compliance & Proper Operation.

It is also interesting to note that the IPC ignored AWWA recommendations regarding backflow and required their installation on sprinkler systems. AWWA Manual 14 does not recommend that they be installed on fire sprinkler systems and they recognize that the Alarm check valves required by NFPA 13 (Wet and Dry Pipe) are sufficient for protection of potable water.

In the State of Mississippi, State law stipulates that Backflow IS NOT required on Low Hazard Connections and specificially lists wet and dry pipe sprinkler systems as being exempt from backflow requirements. It does require them if there is nonpotable cross connections such as antifreeze loops and pumps taking suction from non potable sources. State Law went a step further and prohibited any political subdivision in the state from adopting or enforcing any law or policy that is more stringent than the State Law thereby negating IPC requirements for Backflow on wet and dry pipe sprinkler systems.

I am not a big fan of these devices as you may have noticed. They do have their place but my experience with these devices is that they never are maintained and tested for the use they are intended to serve and they are unreliable when connected to fire sprinkler systems and especially so when placed on lines serving fire hydrants.

We had one installed on a resort complex and when we went to do annual fire pump testing we could not achieve light hazard flow from the system. The connection was one block away from the city’s well.

We had another one installed on private fire service mains and could not achieve 4 head criteria on a 13R system nor could we achieve any usable fire flow from the hydrants serving the apartments. The city main serving this private system system was at a 10 inch/12 inch circulating main crossroads.

So I am not a big fan of these and this article is good in that it points out the need is positively there to not only install the testing means, but fire inspectors do need to enforce the testing provisons of these devices.

This was added in the 1996 NFPA 13 in section 8-2.6 The backflow prevention assembly shall be forward flow tested to ensure proper operation. The minimum flow rate shall be the system demand, including hose stream demand where applicable. The requirement was also added to the 2007 NFPA 24 in section 10.10.2.5.

I would like to make a comment in regard to Mr. Dove’s comment. I agree with Mr. Dove that backflow prevention devices are not needed to protect potable water systems just as he states. Also, it is required by NFPA codes and standards that equipment used in water-based fire protection systems be LISTED. To my knowledge, backflow preventers are not listed but only CLASSIFIED as to water flow characteristics and the strength of body. Backflow preventers, to my knowledge, have not been tested or listed for the rigors of a fire department’s pumping operations applying high pressures to the fire line and the backflow device is used as a check valve. I would like to hear other opinions on this and if there are any backflow prevention devices that are listed, I would like to know that also. I appreciate the opportunity to express a concern I’ve had for a long time. Sincerely, M.J. (Mike) Saade – Fire Protection Engineer & Fire Inspector for the State of Georgia

How do you recommend testing (if any) on an existing system where the sprinkler contractor has changed sprinkler heads to meet a higher density demand. The existing system did not have any means to test foward flow of the back flow preventor.

Brian, there are a couple options, they can utilize an existing connection on the end of a main, they can remove the check valve on the FDC (replace it when done), and test through the FDC. The key is during plan review to mention on an existing system there needs to be an upgrade

I’m very glad I witnessed a forward flow test…..the contractors found no water pressure after opening all the valves…….turns out a sub-contractor for the city failed to open a few sectional valves on one of the city mains after making a repair for an unrelated hydrant…potentially, no one would have known of this problem until, hopefully the main drain test was done a year later!!

From the article above, forward flow testing of backflow preventers is measured with a pitot gauge utilized to ensure the design flow is met.

Latest NFPA 25 changes to para. 13.6.2.1 will delete the current “implied” requirement to measure the flow rate when forward flow testing a backflow preventer, if approved. (nfpa.org – http://www.nfpa.org/onlinepreview/online_preview_document.asp?id=2511# Comments are allowed thru August 31)
If you don’t measure the flow rate, how do you know that you’re getting the design flow rate?
I like the idea presented in Insurance LC rep’s comment above, of measuring the flow rate and comparing the pressure drop with the curve. Without measuring the flow rate, how do you know the pressure drop matches the curve?

The full forward flow test is also required per Unified Facility Criteria 3-601-02 dated 08 September 2010, Page 50, Table 2-26. I see about 40% of the systems failing to meet minimum BOR at the minimum calculated flow requirement.